I think the problem is that the original chainring is about 3mm thick where it bolts to the crank arm and the BBB one is 4.5mm. Below is a photo showing the gap where the chainring will not sit flush against the mounting points, and a diagram attempting to explain where the problem is.

I've had a look at Campy tech docs and can't find anywhere specifying the width of the chainrings at that point. I assume the BBB one just isn't compatible. Or have I missed something?

2 Answers
2

When Campagnolo introduced their 11 speed high end groupsets they re-engineered the chainset and introduced 'Micro Precision Shifting' and that new bottom bracket design amongst other features. Whilst they were at it they put the new (and thinner) chainrings on the 9/10 speed groupsets, including yours. Not that yours is compatible with 11 speed - you would have to replace the chainrings for that.

And yes, they have created a bewildering array of parts that are a compatibility minefield, making one suspect Shimano are not so bad after all...

Your BBB chainring is for the earlier 9/10 speed systems and sadly won't fit. Your best option is to put the 53T back on there until you can devote the man-months needed to research, afford and buy a genuine 50T Campagnolo MPS chainring.

Thanks for that! Trouble is there is no genuine 50T Campagnolo 135BCD chainring. Only the compact, which is 110BCD. I think my only option is to buy a whole compact crankset.
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MacSep 19 '11 at 21:42

I recommend that you actually write to Campagnolo with the model year + model and see what they suggest. Their product line up is getting to be only knowable by high priests (and marketeers).
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ʍǝɥʇɐɯSep 19 '11 at 22:19

I think the article is talking about the width of the teeth. My question is more about the width at the point it attaches to the crank, although I can see that I didn't make that clear... I'll go edit the question
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MacSep 19 '11 at 6:25